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Masonry structures constitute the great majority of buildings in historical centers where construction activities were carried out by adding structural portions to pre-existing ones: as a result, masonry aggregates are currently the most common structural typology in such contexts. The structural behavior of masonry aggregates, which are complex systems of different buildings interacting with each other, is generally affected by several factors, such as the different steps of construction, uncertainties about interlocking between walls, presence of different and irregular masonry textures and multi-leaf walls, which make such a structural typology very difficult to study. During recent seismic events in Italy, a wide number of local collapses has been observed in masonry aggregates of historical centers, highlighting the important role of local mechanisms in the seismic assessment of such structures. In this paper, an efficient software called ANUB-Aggregates (Adaptive Nurbs Upper Bound limit analysis for masonry Aggregates) is proposed for the seismic assessment of partial failure mechanisms in historical masonry aggregates. The theoretical core of this program is a kinematic NURBS-based limit analysis with meta-heuristic mesh adaptation. The use of NURBS allows studying aggregates containing vaulted structures, or any other typology of curved elements, without additional computational effort. Moreover, the mesh adaptation scheme assures the representation of the correct collapse mechanism by finding the real position of fracture lines. Starting from the three-dimensional model of the whole aggregate, the code ANUB-Aggregates provides the analysis of more macro-elements interacting with each other with different interlocking hypotheses, evaluating both simple and complex failure mechanisms. As proof of the effectiveness of this applicative, the analysis of two historical masonry aggregates is presented. [ABSTRACT FROM AUTHOR]

Two new computational algorithms for the Limit Analysis (LA) of large-scale 3D truss-frame structures recently proposed by the authors are reconsidered and adapted for a comparison prediction of the elastoplastic response of a strategic beautiful historic infrastructure, namely the Paderno d'Adda bridge (or San Michele bridge), a riveted wrought iron railway viaduct that was built in northern Italy in 1889. The first LA algorithm traces a fully exact evolutive piece-wise linear elastoplastic response of the structure, up to plastic collapse, by reconstructing the true sequence of activation of made-available plastic joints (as a generalization of plastic hinges), in the true spirit of LA. The second LA algorithm develops an independent kinematic iterative approach apt to directly determine the plastic collapse state, in terms of collapse load multiplier and plastic mechanism, based on the upper-bound theorem of LA. Specifically, the marvelous doubly built-in parabolic arch of the bridge is analyzed, under a static loading configuration at try-out stage, and its elastoplastic response is investigated, in terms of evolutive load-displacement curve, collapse load multiplier and plastic collapse mechanism. The two LA algorithms are found to much effectively run and perform, despite the rather large size of the computational model, with a number of dofs in the order of four thousands, by achieving good corresponding matches in terms of the estimate of the load-bearing capacity and of the collapse characteristics of the arch substructure, showing this to constitute a well-set structural element. Moreover, the direct kinematic method displays a rather dramatic performance, in truly precipitating from above onto the collapse load multiplier and rapidly adjusting to the collapse mode, in very few iterations, by a considerable saving of computational time, with respect to the complete evolutive elastoplastic analysis. This shall open up the way for further adoption of such advanced LA tools, with LA regaining a new momentum within the modern optimization analysis of structural design and form-finding problems. [ABSTRACT FROM AUTHOR]

This study presents the results of the static and dynamic assessment of the dome of the Basilica of Santa Maria degli Angeli in Assisi, designed by Galeazzo Alessi. The first section is devoted to an overview of the masonry domes designed by the Italian architect and focuses on the structural solutions adopted in the several cases described to better understand Alessi’s designing skills. In the second part, the drum-dome system is analyzed in order to attain a structural assessment. The static assessment is performed by means of limit analysis and finite element model approaches with non-linear mechanical behavior. The obtained results are consistent with the detected crack pattern and confirm the suitability of the reinforcement steel rings applied to the drum. The seismic assessment has been performed by response spectrum analysis. Due to the lack of specific information, a probabilistic approach for the material mechanical properties was used. The results obtained highlight an adequate seismic response of the structure that can be attributed to the dynamic properties of the slender drum-dome system. This finding justifies the good performance of the structure during the seismic events of 1832 and 1997. [ABSTRACT FROM PUBLISHER]

Abstract: This paper discusses the cracking pattern in a historical Italian palace proposing a diagnosis for the origin of the actual damage state. The analyzed building, which dates back to the seventeenth century, is a masonry building with a rectangular plan section located in Piancastagnaio (South Tuscany, Italy). The building exhibits a severe and variegated vertical and horizontal cracking pattern mainly affecting the southern and eastern façades. Due to the damage, the palace was evacuated by the Public Authorities during the 1980s and a series of provisional remedies (mainly steel chains) was added. Through the use of the finite element technique, the paper provides an interpretation of the manifested damage. The aim of the diagnosis, supported by the numerical results, is to design an extensive in-situ investigation on the palace. Moreover, the paper aims at evaluating the effectiveness of the actual temporary retrofitting (mainly steel chains) used to freeze the present damage. At the end of the paper the in-situ investigation is presented and discussed. [Copyright &y& Elsevier]

With its internal axes of 37.23 by 24.89 m, the dome of the Sanctuary of Vicoforte, Italy, is the fifth biggest in the world in absolute terms, and by far the largest elliptical dome ever built. The dome-drum system has suffered since the beginning from significant structural problems, partly due to soil settlements, and, to a considerable extent, arising from its bold structural configuration. This article deals with the modeling strategies adopted in the assessment of the structural reliability of the monument, a project undertaken in recent years following the strengthening intervention operated in 1985 with the application of active tie-bars around the perimeter at the top of the drum. The structural behavior of the construction was modeled according to two different approaches: limit analysis and finite element analysis based on linear and non-linear constitutive models for the masonry. [ABSTRACT FROM AUTHOR]

The definition of structural safety of a historical masonry structure is still a concept that is somewhat difficult to interpret. Whereas for new masonry structures, it is possible to have useful indications about their structural behavior, as the analysis turns to “historical” constructions such a task became increasingly more difficult. Furthermore, the needs of preservation of the historical, cultural, and architectural essence of the building in many cases contrast with the needs of providing the “adequate” capacity to its structure, especially in order to withstand the design seismic loads. The study presented in the article is related to the definition of a knowledge and safety assessment path, concerning masonry religious buildings with a monumental character. A complex building, the Santa Maria Assunta (Our Lady of the Assumption) Cathedral in Reggio Emilia (Italy), is studied in order to evaluate its structural behavior thus defining its seismic vulnerability, by using different investigation and analysis methodologies. [ABSTRACT FROM AUTHOR]